When motor-cars were first invented, they were sometimes called horseless carriages, so naturally some early automobiles were designed to look (as far as possible) like a horse and carriage without the horse. We may be in danger of making similar errors. Some Doppler Navigators appear designed to perpetuate methods of navigation which doppler itself should help to render obsolete.

Basically, the doppler phenomenon, measured in the aircraft, gives the aircraft's velocity relative to the reflecting terrain as a vector referenced to the aircraft's axes. In other words, angle of attack, drift and ground-speed are measured directly.

The possible application of this information to improved methods of aircraft operation is almost infinite in its variety. The ways of applying, for example, accurately measured angle of attack, to the take-off, approach and landing phases, or to performance analysis, are numerous. Perhaps the most wildly esoteric suggestion for the application of angle of attack information was that aircraft could be weighed in flight by doppler given equivalent air-speed and the lift/drag polar of the aircraft; unfortunately the question of how to obtain a usable accuracy was not precisely explained! Of course, if sufficient accuracy were possible in this application, we could have a rather novel fuel flow-meter since, on all well conducted flights, fuel flow = rate of change of aircraft weight.